Halfway through the ACC basketball schedule, Virginia's first NCAA tournament bid in five years seems, at first blush, assured. The 18-4 Cavaliers are ranked in both national polls, boast quality wins and have no inexplicable defeats.

But there are Pennsylvania Turnpike-sized potholes ahead — Wednesday's home game against Wake Forest should not be among them — that could knock Virginia into a roadside ditch.

Second, while this marks the Cavaliers' eighth consecutive week in the media and coaches' top 25, they are a modest 42nd in the Rating Percentage Index rankings used by the NCAA tournament selection committee.

And a top-50 RPI hardly assures a bid. In the last five years, the NCAA committee bypassed 30 top-50 teams.

That group includes not only mid-majors such as Missouri State, St. Mary's and Cleveland State, but also power conference types such as Florida State, Clemson, Ohio State and Syracuse.

Even last season, when the field expanded from 65 to 68 teams, five among the top 50 were disappointed on Selection Sunday.

The contrast in Virginia's poll (19th media, 20th coaches) and RPI rankings is rooted in a crucial RPI component: non-conference strength-of-schedule. Virginia Tech fans know the concept all too well, since a tame outside schedule cost the Hokies at least one NCAA bid in the last four years.

The Cavaliers' NCSOS is 248th out of 344 Division I teams. Clemson is the only ACC team lower, at 255. Six league teams, led by Duke at No. 4 and including Virginia Tech at No. 76, are among the top 100 in NCSOS.

The irony is that Virginia's signature win is a non-conference conquest of No. 15 Michigan in the ACC-Big Ten Challenge. But seven of the Cavaliers' 13 outside victories are against teams below 200th on the RPI.

That schedule notwithstanding, Virginia's NCAA credentials to date are solid. With victories over Michigan and Miami, and losses to Duke and Florida State, the Cavaliers are 2-2 against the top 50. They are 6-3 versus the top 100, have five true road wins, and their worst loss is to No. 101 Texas Christian.

So the question becomes, what must Virginia do during the next month to make Selection Sunday stress-free?

The question is a perennial for dozens of teams and is impossible to answer definitively.

Would the Cavaliers (5-3 ACC) make the field at 8-8? Depends on who the other three wins were against, the credentials of other contenders and how Virginia fared in the ACC tournament. Same goes for 9-7.

A winning ACC record used to virtually assure an NCAA invitation, but since the conference expanded in 2004 and abandoned its double round-robin scheduling, all bets are off. Virginia Tech three times and Florida State once have missed the NCAA tournament since 2005 with ACC records of 9-7 or, in the Hokies' case two years ago, 10-6.